Spectrum Engineering

Dedicated short-range communication (DSRC) systems have been proposed for operation at locations across the United States in the 5850- to 5925-MHz band. To establish electromagnetic compatibility between DSRC and other 5-GHz systems, it is necessary to understand current and future occupancy of this spectrum. This report summarizes results of measurements made in 5-GHz spectrum for the Federal Highway Administration (FHWA) of emissions from high-power radars and a fixed satellite service (FSS) earth station.

The Coast Guard plans to operate an Automatic Identification System (AIS) Digital Selective Calling (DSC) based transponder system as part of the Ports and Waterways Safety System (PAWSS) in the lower Mississippi River. The AIS uses two duplex channels for ship-to-shore and shore-to-ship digital data transmissions and a simplex channel for channel management. The duplex channels are identified as AIS working channels. The PAWSS relies on a combination of voice and AIS working channels in the VHF maritime mobile band to provide signal coverage in the vessel traffic service area (VTSA). The proposed coverage area for the VTSA encompasses the Mississippi river starting at river mile 255 to the sea buoy located at Southwest Pass and also includes an area in the Gulf of Mexico for ships approaching the sea buoy. Other waterways such as the Mississippi River Gulf Outlet and the Industrial Canal are also included in the proposed VTSA. A contractor has installed government owned equipment at five tower sites along the river to provide the coverage for both the voice and AIS working channels. Each tower provides coverage for part of the VTSA. Before the system can reach operational status, the coverage of the RF portion of the system must be measured and documented. The Coast Guard funded NTIA to perform coverage tests on the system to examine and evaluate the adequacy of the RF coverage of the channels used for voice and AIS data transmissions. The tests were performed August 4-10, 1999. The results of these tests are given in the following sections of this report.

The Coast Guard funded the National Telecommunications and Information Administration (NTIA) to perform electromagnetic compatibility (EMC) tests between an ITU-R M. 825-3 (Characteristics Of a Transponder System Using Digital Selective Calling Techniques for Use with Vessel Traffic Services and Ship-to Ship Identification) based Automatic Identification System (AIS) operating on 12.5 kHz channels and Public Correspondence (PC) Systems operating on 25 kHz channels. The tests were performed between January 17-28, 2000 in and around an AIS base station communications tower located at Point Ala Hache, La. by NTIA, SETA Corporation, and Coast Guard personnel.